A specialist police unit has shut down more than 2,500 websites selling counterfeit goods believed to be worth tens of millions of pounds.

The sites promised authentic designer goods such as Gucci products, GHD hair straighteners, Ugg boots and Hollister clothing. But customers were left short-changed as the items were either poor quality counterfeits or were never delivered.

The police intellectual property crime unit (Pipcu) was launched by City of London police last September and the number of websites suspended by the unit was announced to coincide with World Intellectual Property Day.

DCI Andy Fyfe, head of Pipcu, said: "The fact Pipcu can announce on World IP Day that in the eight months since launching we have suspended more than 2,500 infringing websites is further evidence of the expertise of our officers and the level of their commitment to clamp down on IP crime. Behind many of these websites lies an organised crime gang funnelling off the money spent by unsuspecting customers on what they think are quality products.

"Consumers also need to be aware that by accessing websites like this they are running the risk of their personal details being compromised and being used for other fraudulent scams, as well as exposing their computer to malicious malware."

Clare Harvell, 42, from Cheshire, was a victim of counterfeit fraud from one of the websites the unit has now suspended. She ordered a pair of UGG boots as a Christmas present for her daughter after clicking on a site that was "listed at the top" of a Google search.

The site had "high quality images", she said, and it "looked and sounded legitimate". But when the boots arrived she was disappointed. "They looked really cheap. In fact the seller had valued them on packaging as only being worth £17, when in fact I had paid over £70 for them. They were wrapped in cardboard and weren't even in a box," she said.

Harvell was able to claim a refund from her credit card company, but she said the issue was ongoing as the website owner had tried to use her card details again.